Meridional asymmetry in recent Pacific sea surface height trends

Recent sea surface height (SSH) trends in the South Pacific are substantially greater than trends in the Northern Hemisphere. Version 4 of the data-constrained ocean state estimate from the Estimating the Climate and Circulation of the Ocean consortium (ECCOv4) reproduces the spatial structure in observed SSH trends, which allows for a diagnosis of the forcing and mechanisms that account for meridional asymmetry in the rate of change. Thermosteric contributions dominate the spatial structure in Pacific SSH trends from ECCOv4, and an analysis of closed temperature budgets from model fields suggest that both surface flux and advective terms contribute to the overall basin-wide trend pattern. We use a model hierarchy of increasing complexity to explore the underlying dynamical processes. A wind-driven, cross-equatorial advective temperature flux leads to a warming of the upper ocean in the tropical South Pacific at the expense of the tropical North Pacific. This wind-driven meridional sea-saw accounts for up to half of the SSH trend amplitude at locations within 30º of the equator in the Pacific, and a reversal in forcing associated with this process could have important implications for near-term rates of coastal sea level change, particularly in Pacific Island communities.